Environmentally constrained modeling of mid-frequency transmission loss and reverberation measured during the Target and Reverberation Experiment 2013

The goal of the Target and Reverberation Experiment (TREX13) was to make contemporaneous measurements of mid-frequency (1.5–4 kHz) transmission loss and reverberation with extensive environmental measurements so detailed model/data comparison can be achieved and important environmental factors can be identified for different applications. APL-UW collaborated with ARL-Penn State, led by John R. Preston, to deploy the Five Octave Research Array (FORA) on a “clothesline” about 2.1 m above the seafloor. This fixed-source/receiver configuration helped eliminate uncertainties from the motion of a towed array and allow reverberation measurement along a narrow, 7-km-long section of seafloor. The experiment site had a fairly complex spatial distribution of both sediment type and sediment scattering properties and keeping the FORA in a fixed position was instrumental in understanding and modeling the reverberation. While soft sediments make up only 27% of the sediments by area at the site, it is necessary to account for this spatial dependence so that both transmission loss and reverberation can be modeled using a consistent set of environmental inputs. These models and their implications for our understanding of the environmental factors which most impact mid-frequency reverberation will be discussed. [Work supported by the U.S. Office of Naval Research.]